Dallas had an issue with 18B20, 18S20, 18B20-PAR, and 18S20-PAR devices, 
known famously as the "C3" Die problem, some time ago.  It is 
characterized, as I am told, by repeated 85C readings returned from the 
device caused by a failure of the chip to properly POR.  The fix 
involves issuing an "exit from test mode" command prior to a conversion.

Reset
issue ROM Command (Skip, Match)
issue 0x64

I haven't seen this problem in new stock so perhaps the best fix is to 
replace the device in question.  However I do cover this in my software 
and perhaps 1WFS might, too.

/m

Paul Alfille wrote:
> 85 (the AA00 bit pattern) is apparently one of the error modes of the 
> chip. We repeat the measurement if it occurs. Then return the value (it 
> COULD be correct). I don't know how to improve. Perhaps power issues? 
> Purely a guess.
> 
> Paul
> 


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